Telephone-repeater monitoring system



TELEPHONE REPEATER MONITORING SYSTEM Dec. 8, 1925-.

R. s. WILBUR Fild June 18, 1921' 4 5 LW. 7 5W W hven/ar: Ray 5. W/Yfiur.

2 Jim.

Patented Dec. 8, 1925.

iiNlTED STATES BAY SETH WILBUR, OF LYNDHURST, NEW

PATENT OFFICE.

JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK,N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-BEPEATER MONITORING SYSTEM.

Application filed .l'une 18,

To all whom it may concern:

Be it known that I, RAY S..W1LBUR, a citizen of the United States,residing at Lyndhurst, in the county of Bergen, State of New Jersey,have invented certain new and useful Improvements in TelephoneRepeaterMonitoring Systems, of which the following is a full, clear, concise,and exact description.

The present invention relatesto monitoring circuits for telephonerepeating stations and like purposes.

An object of the invention is to provide a simplified type of monitoringcircuit suitable for listening in on transmissions passing through arepeating station, without disturbing the normal operation oftherepeater. A further object is to provide a combined monitorin circuitand communication channel, or example over either line section cominginto atwo-way repeating station, and particularly between two separatedrepeating stations, over which channel an at: tendant at a distantstation may be called into conversation from another station on theline.

For this purpose the system of the invention provides preferably at eachrepeating station on a line one or more sources of suitable ringingcurrent, talking and listening sets and simplified switchingarrangements, by which listening, talkin and signalling can be carriedon over eit er or both'sections of the line with facility and despatcli.

A. feature of the invention is theslmple and economical way in which themonitoring and signalling apparatus is coupled to one or theseveral'line circuits. It is desirable to associate. monitoringequipment with the output circuit as then a satisfactory volume ofmonitoring current maybe secured without appreciably reducingthev'norm'altransmission. Heretofore listening-in or monitoring setsdesigned for use with repeater circuits in which the output transformeris made the balanced coil, have required extra re eating coilsinsertedfin the line sections. hese are expensive tdggbuild and have thedisadvantage t at they must be 1921. Serial No. 478,194

balanced in the same way that the other elements of a line must bebalanced. Furthermore the primary windings of such coils are always inthe line Whether the monitoring sets are being used or not, with thenecessary resulting. transmission loss and complications.

The present invention, however, employs simply a few turns of wire onthe usual balanced repeater coil itself to serve as an extra winding.for the monitoring apparatus. This wmdingcan be applied readily duringthe manufacture of the coil, and in fact it a .coil is not the balancedcoil but is used in brid e. In that case it saves the use of an auxiiary coilto avoid metallic connection between the repeater circuit andthe monitoring set.

For a more com lete disclosure of the invention and its mo e ofoperation, a description' of a typical repeater circuit embodying theinvention will now be iven, reference bein had to the accompanyingdrawing in whic Fig. 1 shows a schematic circuit arrangement of therepeating station'for one line; Fig. 2 shows an alternative manner ofassociating the monitorin windingwith the line; and ig. 3 shows aifl'erent manner of applying the monitoring winding.

The line is shown as divided into the usunl east-west sections LE and LWassociated with each other through two one-way rePeat- -ing paths RE andRW. To prevent circulation of energy around the repeating paths the linesections are provided with the usual balancing circuits BE and BWandwith the balanced repeating coils comprising the series line windings 1,2, 3 and 4 associated with the repeater output coils 5, 6. All of thisapparatus is well known in the art and it is clear that with proper linebalances transmissions may, pass from section. LE through the repeaterRW and on to the line LW without finding their way into the input of therepeater RE and similarly transmissions inay pass in the oppositedirection through repeater RE.

According to the form of the invention shown in Fi 1 an extra windingcomprising sections 1 and'8 is applied to the balanced repeating coil toserve for monitoring and signalling. In construction this winding maycomprise a relatively small number of turns of fine wire and may besituated next-to the core or between the primary and secondary windingsor outsidev of the primary and secondary'windings. It thus occupieslittle space and its presence. does not therefore interfere with theeflicient design of the output transformer for its usual an normalfunction. y

The terminals of the windings 7," 8 are brought out to the respectivejacks JE and JW to connect the monitoring apparatus with the line. Theplugs 9 and 10 will be inserted into their respective jacks and fornormal listening over both lines the key K will be thrown to its upperposition where it may if desired be locked thus holding its springs intheir separated positions. A circuit then exists including themonitoring windings 7 and 8 of line LW, springof jack JW, tip of plug 9,contact 11 now clesed, contacts 12 and 13 normally closed, the.resistance R, attendants receiver 20, contacts 14 and 15 normallyclosed, contact 16 of key K, sleeve contacts of plug 10 and jack JE,windings 7 and 8 of line LE, spring and tip of plug 10. contact 17,sleeve contacts of plug 9 and jack JW to the opposite terminal ofmonitoring windings 7 and 8 of line LW. With this circuit establishedthe attendant can listen to transmissions passing over either linesection. The windings 7 and 8 are related to the line windings 1, 2, 3,and 4 in the same manner as are the repeater output windings 5 and 6,and the windings 7 and 8 serve, therefore, to receive currents incomingover the line, or to transmit current over the line, or to receivecurrents from the repeater output windings 5 and 6. Current impressed onthe windings 7 and 8 from the monitoring circuits will not, however,affect the input of the repeater, since they are applied to the lineside and line-balance side of the input terminal in the same manner as"are the repeater output coils 5 and 6. With the circuit established asabove traced, therefore, if the repeaters are operative, the attendanthears signals due to received unamplified current over one line sectionand the same current after it is passed through a repeater and thereforebecome amplified, since the two monitoring coils are connected inseries.

The object of the resistance R is to make the impedance of the receivercircuit,-as used in the monitoring connection, so high that only a smallfraction of the outgoing transmission is drawn ofl into the monitoringreceiver through the windings 7-8. If only one hundredth of the outgoingenergy is drawn off through this circuit the volume of monitoringtransmission will still be as great as that heard on the average by thesubscriber at the distant end. When this is done the impedance of themonitoring circuit is relatively high as compared to that of windings 78and the connection of the monitoringmircuit changes conditions onlyslightly from that of leaving this winding open circuited. On the otherhand the impedance of the talking sets should be designed to match thatof the monitoring connection to afford an veflicient communicationchannel for the repeater attendants.

If the attendant desires to talk over both line sections at onceheleaves the key K in its up position and throws the double throw key DKto the right in the drawing. This separates the key springs openingcontacts l3 and 14 and closes contacts 21 and 22. This alters thecircuit previously traced by establishing a path from contact 11 throughcontact 21, secondary of microphone repeating coil 23, contact 22,contact 16 and from thereon as previously traced. Speech currents set upby the microphone T therefore pass to both line sections but do notafiect the input of either repeater as' described.

When the key DK was thrown 'asdescribed the receiver 20 was cut 011' atcontacts 13 and 14 but is connected across one half of the secondary ofrepeating coil 23 thereby providing side tone in the receiver andfurnishing an eflicie'nt'circuitfor receiving over .either line section.

If 1t is desired to transniit ringing current over both line sections atthe same time, the key DK is thrown to the left in the drawingseparating the left hand springs and opening the contacts 12 and 15 ot'the normal listening circuit and closing contacts 24 and 25'leading toa, source of suitable ringing current RC. From contacts 24 and 25 thecircuit is as previously traced to the monitoring windings of the twoline sections in series. During ringing the attendants transmitter andreceiver are dis connected at contacts of key DK,

If it is desired to listen, talk or ring over line section LE the key Kis thrown to the down position to open its sprin s and the key KE isthrown to the upor c osed position. A circuit then exists from the jackand keys K and KE are opened a circuit is established from themonitoring coil of the line LW, jack JW, plug 9 through the key contactsand 31 to the, common leads 28, 29, for connecting any of the monitoringapparatus desired to the line section LW.

In Fig. 2 isshown a method of positioning telephone repeater stationsemploying a baland utilizing the monitoring windings 7 and 8 which oftenproves convenient. The wind ings 'i" and8 are positioned between theline windings 1, 2, 3, and 4 and the repeater output windings 5 and 6and the mid-point of the windings 7 and 8 is connected directly toground. This provides an eflective electrostatic shieldand acts verymuch as if a groundedmetallic sheath were inserted between the primaryand secondary windings of the balanced repeating coil. If bothmonitoring windings are arranged in this manner a tendency oi therepeater to sing due to electrostatic differences of potentials aroundthe repeater circuit isopposed.

,In each of the Figures 1 and 2 the output of the repeater is associatedwith the outgoing line through the inductively related windings of thebalanced repeating coil. In

some cases the arrangement is to connect the output circuit of therepeater to the bridged circuit of the repeating coil as shown in Fig.3, where the output of repeater RE is connected through transformer 40,41 to the bridged circuit 42. In such a case the moni-' toring windingmay be applied to the output transformer 40, 41, the monitoring windingbeing indicated at 43.

It will be understood that the apparatus I shown at the monitoringstation and the keys for controlling the various connections areillustrative of only one of many possible arran ements and that theprincipal object of idle invention once having been shown it will beobvious that these circuit arrange-- ments may be widely changed to meetvarying conditions without departing from the spirit of the inventionthe scope of. which is defined in the appended claims.

What is'claimed is:

1. In a monitoring and signaling system for a telephone repeaterstation, said repeater station having line sections interconnectedthrough oppositely directed repeaters, a balanced repeater coil for eachof the interconnected line sections, and monitoring .and signaling coilseach comprising an extra anced repeating coil in the line, said circuitcomprising an extra winding inductively re-. rated to the line windingof said repeating coil but out of conductive relation to the circuit, areceiver, a circuit of such high impedance as to have negligiblereaction on the normal repeater action for closing said ex-- tra windingthrough said receiver, a talking set for enabling the monitoringoperator to communicate over the line through said extra winding, saidtalking set being proportioned to such an impedance as to give efiicienttransmission to the connected transmisslon hnes.

4. In a repeater circuit including balanced ;repeater output windingsmounted on a common core, a supervisory winding mounted on said core andin inductive relation to said repeater output windings and circuitarrangements for utilizing said coil for talking and listening purposes.I

5. In a repeating arrangement for a line, a balanced transformer windingincluding in the line circuit, a repeater having its out-- put circuitinductively. coupled to the bal-- anced transformer winding, anauxiliary winding inductively associated with said transformer andsupervisory apparatus connected in circuit with said auxlliary wind mg.

ancing circuit, a repeater input circuit con-- nected to the mid-pointsof said windings, a

repeater ouzcl-put circuit inductively related to said win i no A line,a balancing circuit therefore, transformer windings :n said line andbatngs, an auxiliary winding inductively associated .with said windingsand supervisory apparatus connected in circuit with said auxiliarywinding.

7. A line, a balancing circuit therefor,

transformer windings in said line and bal ancing circuit, a repeaterinput circuit connected to the midoints of said windings, a repeateroutput circuit inductively relatedv to said windings, and an auxiliarywinding inductively associated with said windings and connected incircuit with supervisory apparatus, said auxiliary winding beingbalanced, whereby energy from said an rvisory apparatus dividessubstantially equally 4 Ma awi between said line and said balancingcircuit. circuit, and means for utilizing saicl moni- 8'. A monitoringand signaling circuit for toring and signaling Winding for signalingtelephone repeater stations en'lploying a baland talking purposes. 10anced repeating coil comprising a monitor- In witness whereof, Ihereunto subscribe ing and signaling Winding inductively remy name this15th day of June A; D, 1921. lated to the line windings of saidrepeating coil but out of conductive relation to the line RAY SETHWILBUR.

